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Pulmonary Arteriovenous Malformations: How Do I Embolize?
Pulmonary Arteriovenous Malformations: How Do I Embolize? Robert I. White, Jr., MD Pulmonary arteriovenous malformations (PAVM) are high-flow, low-pressure shunts, consisting of a single feeding artery connecting via an aneurysmal sac to a draining vein. The aneurysmal connection is referred to as an aneurysmal sac. The “filter capacity” of the pulmonary capillaries is lost and results in predisposition to brain abscess, stroke, and transient ischemic attack and, when multiple, dyspnea, because of right-to-left shunting and hypoxemia. PAVM are markers of hereditary hemorrhagic telangiectasia (HHT). Up to 30% of patients with HHT have PAVM complicating their disorder. Left untreated, 50% of patients with PAVM will develop disabling or fatal complications. In addition to stroke and transient ischemic attack syndromes due to passage of paradoxical emboli through the PAVM, rupture of the aneurysmal sac, particularly in the third trimester of pregnancy, can lead to fatal hemoptysis or hemothorax. Finally, brain abscess or more obscure musculoskeletal or spinal infections may be secondary to PAVM. Since detachable silicone balloons are no longer available, we have developed precise techniques for closing pulmonary malformations using pushable fibered coils. It is not the coil that is so important, but it is the use of coaxial or triaxial catheters that allow for precise placement of the coil. Cross-sectional occlusion is essential for embolization of PAVM and this is achieved using the “anchor” or “scaffold” technique. Our recent results indicate permanent involution of treated malformations with a 3% recurrence rate. All patients should be assessed for other manifestations of HHT before treatment and they are best followed in one of the 20 HHT Centers worldwide (www.hht.org). Tech Vasc Interventional Rad 10:283-290 © 2007 Elsevier Inc. All rights reserved. KEYWORDS pulmonary arteriovenous malformation, embolotherapy, anchor, scaffold, fibered coils
P
ulmonary arteriovenous malformations (PAVMs) are abnormal communications between pulmonary arteries and pulmonary veins without an intervening capillary network. While not rare, the condition is relatively uncommon. The majority of PAVMs, between 80 to 90%, occur in patients with hereditary hemorrhagic telangiectasia (HHT), a genetic disorder that causes abnormalities of blood vessels. Between 15 and 30% of patients with HHT have a PAVM and, if left untreated, 50% of PAVM patients will have a stroke, brain abscess, or pulmonary hemorrhage.1 Since the 1990s, embolization has been the treatment of choice for PAVMs, with detachable balloons and detachable or pushable coils being the most commonly used materials. In 2002, however, detachable occlusion balloons were removed from the U.S. market, leaving only detachable and pushable coils as options. Detachable coils had the advantage of a more controlled and safer delivery, with less chance of Yale Vascular Malformation Center, Yale University School of Medicine, New Haven, CT. Address reprint requests to: Robert I. White, Jr., Yale Vascular Malformation Center, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520. E-mail: [email protected].
1089-2516/07/$-see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1053/j.tvir.2008.03.007
coil migration; however, they were considerably more expensive. Therefore, our group developed a new technique of using coaxial catheters to deliver pushable coils. This technique provides a safe and controlled deployment and offers a cost-effective alternative to detachable coils.2,3
Techniques and Methods Patient Selection Criteria In the majority of cases, patients with pulmonary arteriovenous malformations have an underlying genetic disorder of the blood vessels, HHT. Therefore, any PAVM patient who has not been previously diagnosed with HHT should be tested for the disorder. If the patient has HHT, his entire family should receive genetic counseling and possibly screening. The incidence of PAVM is approximately 30 to 40% among family members of a patient with HHT. Because HHT is an autosomal-dominant disorder, each child of an HHTpositive parent has a 50% chance of also having the disorder.4 In our practice, the treatment criterion for a PAVM is an arterial diameter of 3 mm or larger, because we believe 3 mm to be the threshold for passage of thrombi. In addition, these 283
R.I. White
284
Figure 1 (A) The anchor technique is useful for all arteries and veins when there is concern about migration of a pushable fibered coil during placement. Usually cross-sectional occlusion of the vessel is easily accomplished with the addition of one or two more coils. The anchor technique has done away with the need for more expensive detachable coil systems in the treatment of fistulas in the lung or complicated arterial and venous anatomy in other locations. (B-E) Patient presents with a PAVM, which has a 6-mm feeding artery. The anchor vessel is very close to the aneurysmal sac of the PAVM (B). For stability a 7-French LuMax guide catheter is placed in the proximal portion of the pulmonary artery and the coaxial 5-French Slip-Cath is advanced within the anchor vessel. The first 2 cm of an 8-mm Nester embolization coil is placed in the anchor vessel (C). At this point the inner Slip-Cath is gently pulled back into the feeding pulmonary artery while continuing to deploy the first coil (C). Two additional 6-mm Nester coils are packed within the first coil (D). Complete cross-sectional occlusion is achieved and no filling of the PAVM is seen on the final angiogram (E). (Color version of figure is available online.)
Pulmonary arteriovenous malformations
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Figure 2 (A-H) Patient with a PAVM presents for transcatheter occlusion. Initial angiogram was obtained in the left anterior oblique (LAO) projection and while the anchor vessel of choice can be seen it was not in profile (A). An additional angiogram was obtained in the right anterior oblique (RAO) projection, which was preferred as the anchor vessel could not only be seen but was also in profile (B, C). The anchor vessel is shown to be adjacent to both arteries feeding the PAVM. The 5-French Slip-Cath is advanced into the initial portion of the anchor vessel and an 8-mm Nester coil is partially deployed. The guide catheter is held stable while the inner coaxial catheter is slightly withdrawn and while the remainder of the embolization coil is deployed (D-F). Two additional Nester coils (8 and 6 mm) were deployed and complete cross-sectional occlusion was achieved with a total of four coils (G, H). The technique of using a coaxial catheter system provides an extremely stable platform, which improves control and accuracy.
larger PAVMs are more prone to rupture. In 80% of the cases, patients with large PAVMs have smaller ones present as well. While not candidates for embolization, these smaller malformations still pose a risk for infection, air emboli, and brain abscess. Therefore, it is important that patients return for a follow-up chest computed tomography 1 year after occlusion of the larger PAVMs. This allows confirmation that the
treated malformations remain occluded and also enables monitoring of untreated malformations.5,6
Details of Equipment Used Every embolization procedure is preceded by diagnostic pulmonary angiography and measurement of pulmonary artery
R.I. White
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Figure 2 (Continued)
pressures. Pulmonary artery mean pressures should be less than 20 mm Hg. In some patients pulmonary artery pressures are elevated because of associated primary pulmonary hypertension or liver malformations. A 7.0-French sheath is placed in the right or left femoral vein, and a 5.0-French pigtail is passed through it. Once the pressures and angiogram are complete, a 260-cm Rosen exchange wire is advanced through the in situ 5.0
catheter, and the 5.0 catheter is exchanged for a 7.0/5.0 French Lumax Guiding Catheter (Cook Medical, Bloomington, IN). In approximately 90% of our cases, the 7.0/ 5.0 French coaxial Lumax catheter is used to complete the embolization procedure. Sometimes, we substitute other inner catheters to facilitate occlusion of the PAVM. With the 80-cm 7.0 French guide catheter positioned in the feeding artery to the PAVM, it is easy to exchange the
Pulmonary arteriovenous malformations 5.0-French 100-cm inner catheter for other catheters. Following treatment of each lung, the inner 5.0-French catheter is replaced with a 5.0-French pigtail catheter for a completion angiogram. When access to the right middle lobe or lingula of the lung is required, we commonly substitute a 5.0-French 100-cm left coronary catheter, Judkins configuration (Cordis Corporation, Miami, FL), for the 5.0-French Lumax inner catheter. Once access to the right middle lobe or lingula has been achieved, the 7.0-French guiding catheter may be advanced over the 5.0-French Cordis. The Cordis catheter may be exchanged for a Cook 5.0-French catheter or a Terumo 5.0French angled Glide catheter for use with 0.035 coils or for smaller PAVMs; we may pass triaxially a microcatheter and occlude the PAVM. We use a variety of stainless steel, platinum, and Inconel fibered pushable coils, including Tornado and Nester coils (Cook Medical), Trufill coils (Cordis), and Diamond and Vortex coils (Boston Scientific Corporation, Natick, MA). However, we have found that the choice of coil is less important than the use of a guiding catheter to achieve stable placement in the artery or vein to be occluded.
Preferred Approach Most patients are seen in the IR clinic before the PAVM embolization procedure, to anticipate complicated situations which may require medical consult. The procedure itself is performed on an outpatient basis, except in patients who exhibit comorbidities such as heart disease, severe chronic lung disease, or other pathologies that put them at a higher risk. Typically, the patient is heparinized in a single dose of 100 units/kg. We believe it is critical to obtain pulmonary artery pressures as mentioned under the technique section. Most patients with PAVM have low pulmonary vascular resistance and pressure but there are important exceptions. Type 2 HHT patients may have primary pulmonary hypertension. All HHT patients may have mild to moderate pulmonary hypertension due to liver arteriovenous malformations or other causes. Measuring pulmonary artery pressures and understanding their significance is important before treating pulmonary malformations.7,8 In patients with multiple bilateral PAVMs, our preference is to treat only one lung at a time. There are a number of reasons for this, the first simply being the length of the procedure (2-3 hours per lung). Patient comfort is another consideration. Approximately 20% of patients experience pleurisy after the procedure, and it is less painful for these patients to have only one lung affected. A final reason is that when the patient returns in 4 to 6 weeks for the second procedure, we have an opportunity to evaluate the previously treated lung by angiography. As noted earlier, the most important factor in successful PAVM occlusion is a properly placed guiding catheter. The use of a guiding catheter avoids elongation of the coil during deployment, resulting in a more tightly packed mass of coils and better cross-sectional occlusion of the vessel. More importantly, guiding catheters provide enhanced stability and control during coil deployment. This added control allows us to employ two highly effective deployment techniques: the anchor technique and the scaffold technique. In our experi-
287
Figure 3 Deployment of initial high radial force MReye embolization coils allows for the creation of a solid scaffold. This scaffold provides us with an “endoskeleton,” allowing for softer platinum embolization coils to then be packed within the “endoskeleton” completing the occlusion. (Color version of figure is available online.)
ence, 90% of PAVMs are effectively occluded using one of these two approaches. Anchor Technique9 In the anchor technique (Figs. 1 and 2), the guiding catheter is placed in the artery targeted for occlusion, and the inner catheter is advanced into a side branch as close as possible to the aneurysmal sac. The first 2 cm of a long coil is deployed in the side branch, and the remainder of the coil is deployed just proximal to the side branch, packed into a tight mass. Additional coils may then be woven into the mass. Securing the initial coil in the manner described avoids the potential for coil migration and paradoxical embolization through the PAVM. It also allows for controlled deployment of the remainder of the coil. As subsequent coils are deployed, the guiding catheter enables tight, compact coiling that ultimately creates cross-sectional occlusion, similar to that achieved by a balloon. Scaffold Technique9 (Fig. 3) In high-flow fistulas with large arteries, cross-sectional occlusion can be achieved by first creating a matrix of a long high radial force fibered stainless steel or Inconel coil. These first coils should be 2 mm larger than the artery and may be anchored in a side branch if there is concern about fixation. Once the initial, high radial force coils have been deployed, it may be desirable to position several smaller diameter high radial force coils within the matrix as well. Subsequently, softer, fibered platinum coils can be woven into the matrix until complete occlusion is attained. In 10% of patients, with high-flow arteries or very largediameter arteries, the embolization procedure is initiated through an occlusion balloon that has been temporarily inflated to block flow (Fig. 4). Once the first coils are placed, creating a scaffold, the balloon is deflated and exchanged for a standard coaxial guiding catheter. Long-fibered platinum coils are then delivered through the coaxial catheter until occlusion is achieved.10
R.I. White
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Figure 4 (A-F) Scaffold technique. This technique is used for large PAVMs with arteries greater than 8 mm in diameter. In this patient, an elderly woman with liver malformations and moderate pulmonary hypertension, it was thought safer to place the high radial force coils through an occlusion balloon catheter. (A) shows the arterial phase of a selective pulmonary angiogram in the feeding artery to the malformation. The pulmonary artery pressures were 50/20, reflecting the underlying high flow liver malformations. In (B), the 7/5 Lumax guiding catheter (Cook, Bloomington, IN) was used to attempt to identify a suitable anchor vessel near the aneurysmal sac. None was found. In (C), a 20-mm occlusion balloon catheter (Boston Scientific, Natick, MA) was placed in the feeding artery and inflated. The patient was heparinized during the procedure. Oversized stainless steel coils of 15-, 12-, and 10-mm diameter were placed in the feeding artery to form an “endoskeleton” or “scaffold.” Once the “scaffold” is formed, the occlusion balloon catheter is deflated and the 7/5 Lumax catheter is exchanged for it. Cross-sectional occlusion is obtained by nesting long platinum fibered coils within the “scaffold.” In (D, E), the final occlusion is demonstrated. In (F, G), an 8-month follow-up demonstrates no reperfusion. In patients with pulmonary hypertension, reperfusion is more common and it is our practice to perform a follow-up pulmonary angiogram at 6 months to 1 year. (Color version of figure is available online.)
Technical Suggestions We have identified a number of key practices that we believe contribute to technical success and significantly reduce complications. First, we have found it best to deliberate over options rather than to respond immediately, in elective patients with PAVMs in larger arteries. It is beneficial to perform a diagnostic angiogram first and then take time to evaluate the results and determine the most effective approach.3,11
We also recommend that wires always be withdrawn from catheters under saline. This prevents the possibility of air entering the catheter as the wire is withdrawn and avoids the potential of air emboli. In addition, regular flushing of catheters serves to reduce the potential for embolization of particular matter or clot. Before injecting contrast material or saline, we ensure that blood can be easily aspirated. If blood cannot be aspirated, move the catheter and test again before
Pulmonary arteriovenous malformations
289
Figure 4 (Continued)
attempting to flushing a catheter. Injection should never be attempted if blood cannot be aspirated.
Results Our results using pushable fibered coils are identical to our results using detachable balloons, with a recurrence rate of 3% per patient and 6% per PAVM. In our use of the anchor and scaffold techniques, we have not experienced paradoxical embolization of coil since 1994.11,12 It is important to note that enlargement of small PAVMs is more common than recurrence of treated PAVMs, occurring in
approximately 18% of patients.3 Most patients with recurrent or enlarged PAVMs are symptomatic; however, this is not always the case and some malformations are only identified with imaging. Therefore, noncontrast computed tomographic (chest computed tomography) evaluation of treated patients is necessary at the 1-year mark and every 5 years thereafter.3
Discussion Up until the early 1990s, thoracic surgeons advocated the surgical removal of PAVMs. In 1997, our group presented our results on
R.I. White
290 occlusion of large PAVMs to the Society of Thoracic Surgeons.11 Since then, embolization has effectively replaced surgery as the treatment of choice. A number of different materials have been used to embolize PAVMs, including detachable occlusion balloons, various types of fibered and unfibered, detachable, and pushable coils, and, most recently, the Amplatzer Vascular Plug (AGA Medical Corporation, Plymouth, MN).13 At the present time, detachable balloons are only available in Europe. They are made of latex with a gold-valve balloon (Nycomed, Paris, France). Published reports on the use of this device indicate problems with early deflation, leading to poor results.14 No other balloons have been available since 2002. The Amplatzer plug has become an attractive alternative among some interventional radiologists; however, the device is costly and long-term results are not yet available.15 There are good long-term data on the various types of fibered pushable coils.3,16 Nonfibered detachable microcoils have been advocated by some; however, they are expensive and do not offer an advantage over pushable fibered coils delivered with our guiding catheter approach.17
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References 1. White RI Jr, Pollak JS, Wirth JA: Pulmonary arteriovenous malformations: diagnosis and transcatheter embolotherapy. JVIR 7:787-804, 1996 2. Mager JJ, Overtoom TT, Blauw H, et al: Embolotherapy of pulmonary arteriovenous malformations: long-term results in 112 patients. J Vasc Interv Radiol 15:451-456, 2004 3. Pollak JS, Saluja S, Thabet A, et al: Clinical and anatomic outcomes after embolotherapy of pulmonary arteriovenous malformations. J Vasc Interv Radiol 17(1):35-45, 2006 4. Guttmacher AE, Marchuk DA, White RI Jr: Hereditary hemorrhagic telangiectasia. New Engl J Med 333:918-924, 1995 5. Hewes RC, Auster M, White RI Jr: Cerebral embolism: first manifestation of pulmonary arteriovenous malformation in patients with
14.
15.
16.
17.
hereditary hemorrhagic telangiectasia. Cardiovasc Intervent Radiol 8:151-155, 1985 Moussouttas M, Fayad P, Rosenblatt M, et al: Pulmonary arteriovenous malformations: cerebral ischemia and neurologic manifestations. Neurology 55:959-964, 2000 Garcia-Tsao G, Korzenik JR, Young L, et al: Liver disease in patients with hereditary hemorrhagic telangiectasia. New Engl J Med 343(13): 931-936, 2000 Trembath RC, Thomson JR, Machado RD, et al: Clinical and molecular genetic features of pulmonary hypertension in patients with hereditary hemorrhagic telangiectasia. New Engl J Med 345(5):325-334, 2001 White RI Jr, Pollak JS: Controlled delivery of pushable fibered coils for large vessel embolotherapy, in: Vascular Ebolotherapy: A Comprehensive Approach. Springer, Heidelberg, Germany, 2006, pp 35-42 Tal MG, Saluja S, Henderson KJ, et al: Vein of Galen technique for occluding the aneurysmal sac of pulmonary arteriovenous malformations. J Vas Interv Radiol 13:1261-1264, 2002 Lee DW, White RI Jr, Egglin TK, et al: Embolotherapy of large pulmonary arteriovenous malformations—long term results. Ann Thorax Surg 64:930-940, 1997 Pollak JS, Saluja S, Thabet A, et al: Clinical and anatomic outcomes after embolotherapy of pulmonary arteriovenous malformations. J Vasc Interv Radiol 17:35-44, 2006 White RI Jr: Re: Bilateral multiple pulmonary arteriovenous malformations: endovascular treatment with the Amplatzer vascular plug. J Vasc Interv Radiol 17(1):141-145, 2006 Saluja S, Sitko I, Lee DW, et al: Embolotherapy of pulmonary arteriovenous malformations with detachable balloons: long-term durability and efficacy. J Vas Interv Radiol 10:883-889, 1999 Ferro C, Rossi UG, Bovio G, et al: Percutaneous transcatheter embolization of a large pulmonary arteriovenous fistula with an Amplatzer vascular plug. Cardiovasc Intervent Radiol 30(2):328-331, 2007 Mager JJ, Zanen P, Verzijlbergen F, et al: Quantification of right-to-left shunt with (99m)Tc-labelled albumin macroaggregates and 100% oxygen in patients with hereditary haemorrhagic telangiectasia. Clin Sci (Lond) 102(2):127-134, 2002 White RI Jr, Pollak JS, Picus D: Are Guglielmi detachable coils necessary for treating pulmonary arteriovenous malformations? Radiology 226(2):599-600, 2003
P
ulmonary arteriovenous malformations (PAVMs) are abnormal communications between pulmonary arteries and pulmonary veins without an intervening capillary network. While not rare, the condition is relatively uncommon. The majority of PAVMs, between 80 to 90%, occur in patients with hereditary hemorrhagic telangiectasia (HHT), a genetic disorder that causes abnormalities of blood vessels. Between 15 and 30% of patients with HHT have a PAVM and, if left untreated, 50% of PAVM patients will have a stroke, brain abscess, or pulmonary hemorrhage.1 Since the 1990s, embolization has been the treatment of choice for PAVMs, with detachable balloons and detachable or pushable coils being the most commonly used materials. In 2002, however, detachable occlusion balloons were removed from the U.S. market, leaving only detachable and pushable coils as options. Detachable coils had the advantage of a more controlled and safer delivery, with less chance of Yale Vascular Malformation Center, Yale University School of Medicine, New Haven, CT. Address reprint requests to: Robert I. White, Jr., Yale Vascular Malformation Center, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520. E-mail: [email protected].
1089-2516/07/$-see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1053/j.tvir.2008.03.007
coil migration; however, they were considerably more expensive. Therefore, our group developed a new technique of using coaxial catheters to deliver pushable coils. This technique provides a safe and controlled deployment and offers a cost-effective alternative to detachable coils.2,3
Techniques and Methods Patient Selection Criteria In the majority of cases, patients with pulmonary arteriovenous malformations have an underlying genetic disorder of the blood vessels, HHT. Therefore, any PAVM patient who has not been previously diagnosed with HHT should be tested for the disorder. If the patient has HHT, his entire family should receive genetic counseling and possibly screening. The incidence of PAVM is approximately 30 to 40% among family members of a patient with HHT. Because HHT is an autosomal-dominant disorder, each child of an HHTpositive parent has a 50% chance of also having the disorder.4 In our practice, the treatment criterion for a PAVM is an arterial diameter of 3 mm or larger, because we believe 3 mm to be the threshold for passage of thrombi. In addition, these 283
R.I. White
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Figure 1 (A) The anchor technique is useful for all arteries and veins when there is concern about migration of a pushable fibered coil during placement. Usually cross-sectional occlusion of the vessel is easily accomplished with the addition of one or two more coils. The anchor technique has done away with the need for more expensive detachable coil systems in the treatment of fistulas in the lung or complicated arterial and venous anatomy in other locations. (B-E) Patient presents with a PAVM, which has a 6-mm feeding artery. The anchor vessel is very close to the aneurysmal sac of the PAVM (B). For stability a 7-French LuMax guide catheter is placed in the proximal portion of the pulmonary artery and the coaxial 5-French Slip-Cath is advanced within the anchor vessel. The first 2 cm of an 8-mm Nester embolization coil is placed in the anchor vessel (C). At this point the inner Slip-Cath is gently pulled back into the feeding pulmonary artery while continuing to deploy the first coil (C). Two additional 6-mm Nester coils are packed within the first coil (D). Complete cross-sectional occlusion is achieved and no filling of the PAVM is seen on the final angiogram (E). (Color version of figure is available online.)
Pulmonary arteriovenous malformations
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Figure 2 (A-H) Patient with a PAVM presents for transcatheter occlusion. Initial angiogram was obtained in the left anterior oblique (LAO) projection and while the anchor vessel of choice can be seen it was not in profile (A). An additional angiogram was obtained in the right anterior oblique (RAO) projection, which was preferred as the anchor vessel could not only be seen but was also in profile (B, C). The anchor vessel is shown to be adjacent to both arteries feeding the PAVM. The 5-French Slip-Cath is advanced into the initial portion of the anchor vessel and an 8-mm Nester coil is partially deployed. The guide catheter is held stable while the inner coaxial catheter is slightly withdrawn and while the remainder of the embolization coil is deployed (D-F). Two additional Nester coils (8 and 6 mm) were deployed and complete cross-sectional occlusion was achieved with a total of four coils (G, H). The technique of using a coaxial catheter system provides an extremely stable platform, which improves control and accuracy.
larger PAVMs are more prone to rupture. In 80% of the cases, patients with large PAVMs have smaller ones present as well. While not candidates for embolization, these smaller malformations still pose a risk for infection, air emboli, and brain abscess. Therefore, it is important that patients return for a follow-up chest computed tomography 1 year after occlusion of the larger PAVMs. This allows confirmation that the
treated malformations remain occluded and also enables monitoring of untreated malformations.5,6
Details of Equipment Used Every embolization procedure is preceded by diagnostic pulmonary angiography and measurement of pulmonary artery
R.I. White
286
Figure 2 (Continued)
pressures. Pulmonary artery mean pressures should be less than 20 mm Hg. In some patients pulmonary artery pressures are elevated because of associated primary pulmonary hypertension or liver malformations. A 7.0-French sheath is placed in the right or left femoral vein, and a 5.0-French pigtail is passed through it. Once the pressures and angiogram are complete, a 260-cm Rosen exchange wire is advanced through the in situ 5.0
catheter, and the 5.0 catheter is exchanged for a 7.0/5.0 French Lumax Guiding Catheter (Cook Medical, Bloomington, IN). In approximately 90% of our cases, the 7.0/ 5.0 French coaxial Lumax catheter is used to complete the embolization procedure. Sometimes, we substitute other inner catheters to facilitate occlusion of the PAVM. With the 80-cm 7.0 French guide catheter positioned in the feeding artery to the PAVM, it is easy to exchange the
Pulmonary arteriovenous malformations 5.0-French 100-cm inner catheter for other catheters. Following treatment of each lung, the inner 5.0-French catheter is replaced with a 5.0-French pigtail catheter for a completion angiogram. When access to the right middle lobe or lingula of the lung is required, we commonly substitute a 5.0-French 100-cm left coronary catheter, Judkins configuration (Cordis Corporation, Miami, FL), for the 5.0-French Lumax inner catheter. Once access to the right middle lobe or lingula has been achieved, the 7.0-French guiding catheter may be advanced over the 5.0-French Cordis. The Cordis catheter may be exchanged for a Cook 5.0-French catheter or a Terumo 5.0French angled Glide catheter for use with 0.035 coils or for smaller PAVMs; we may pass triaxially a microcatheter and occlude the PAVM. We use a variety of stainless steel, platinum, and Inconel fibered pushable coils, including Tornado and Nester coils (Cook Medical), Trufill coils (Cordis), and Diamond and Vortex coils (Boston Scientific Corporation, Natick, MA). However, we have found that the choice of coil is less important than the use of a guiding catheter to achieve stable placement in the artery or vein to be occluded.
Preferred Approach Most patients are seen in the IR clinic before the PAVM embolization procedure, to anticipate complicated situations which may require medical consult. The procedure itself is performed on an outpatient basis, except in patients who exhibit comorbidities such as heart disease, severe chronic lung disease, or other pathologies that put them at a higher risk. Typically, the patient is heparinized in a single dose of 100 units/kg. We believe it is critical to obtain pulmonary artery pressures as mentioned under the technique section. Most patients with PAVM have low pulmonary vascular resistance and pressure but there are important exceptions. Type 2 HHT patients may have primary pulmonary hypertension. All HHT patients may have mild to moderate pulmonary hypertension due to liver arteriovenous malformations or other causes. Measuring pulmonary artery pressures and understanding their significance is important before treating pulmonary malformations.7,8 In patients with multiple bilateral PAVMs, our preference is to treat only one lung at a time. There are a number of reasons for this, the first simply being the length of the procedure (2-3 hours per lung). Patient comfort is another consideration. Approximately 20% of patients experience pleurisy after the procedure, and it is less painful for these patients to have only one lung affected. A final reason is that when the patient returns in 4 to 6 weeks for the second procedure, we have an opportunity to evaluate the previously treated lung by angiography. As noted earlier, the most important factor in successful PAVM occlusion is a properly placed guiding catheter. The use of a guiding catheter avoids elongation of the coil during deployment, resulting in a more tightly packed mass of coils and better cross-sectional occlusion of the vessel. More importantly, guiding catheters provide enhanced stability and control during coil deployment. This added control allows us to employ two highly effective deployment techniques: the anchor technique and the scaffold technique. In our experi-
287
Figure 3 Deployment of initial high radial force MReye embolization coils allows for the creation of a solid scaffold. This scaffold provides us with an “endoskeleton,” allowing for softer platinum embolization coils to then be packed within the “endoskeleton” completing the occlusion. (Color version of figure is available online.)
ence, 90% of PAVMs are effectively occluded using one of these two approaches. Anchor Technique9 In the anchor technique (Figs. 1 and 2), the guiding catheter is placed in the artery targeted for occlusion, and the inner catheter is advanced into a side branch as close as possible to the aneurysmal sac. The first 2 cm of a long coil is deployed in the side branch, and the remainder of the coil is deployed just proximal to the side branch, packed into a tight mass. Additional coils may then be woven into the mass. Securing the initial coil in the manner described avoids the potential for coil migration and paradoxical embolization through the PAVM. It also allows for controlled deployment of the remainder of the coil. As subsequent coils are deployed, the guiding catheter enables tight, compact coiling that ultimately creates cross-sectional occlusion, similar to that achieved by a balloon. Scaffold Technique9 (Fig. 3) In high-flow fistulas with large arteries, cross-sectional occlusion can be achieved by first creating a matrix of a long high radial force fibered stainless steel or Inconel coil. These first coils should be 2 mm larger than the artery and may be anchored in a side branch if there is concern about fixation. Once the initial, high radial force coils have been deployed, it may be desirable to position several smaller diameter high radial force coils within the matrix as well. Subsequently, softer, fibered platinum coils can be woven into the matrix until complete occlusion is attained. In 10% of patients, with high-flow arteries or very largediameter arteries, the embolization procedure is initiated through an occlusion balloon that has been temporarily inflated to block flow (Fig. 4). Once the first coils are placed, creating a scaffold, the balloon is deflated and exchanged for a standard coaxial guiding catheter. Long-fibered platinum coils are then delivered through the coaxial catheter until occlusion is achieved.10
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Figure 4 (A-F) Scaffold technique. This technique is used for large PAVMs with arteries greater than 8 mm in diameter. In this patient, an elderly woman with liver malformations and moderate pulmonary hypertension, it was thought safer to place the high radial force coils through an occlusion balloon catheter. (A) shows the arterial phase of a selective pulmonary angiogram in the feeding artery to the malformation. The pulmonary artery pressures were 50/20, reflecting the underlying high flow liver malformations. In (B), the 7/5 Lumax guiding catheter (Cook, Bloomington, IN) was used to attempt to identify a suitable anchor vessel near the aneurysmal sac. None was found. In (C), a 20-mm occlusion balloon catheter (Boston Scientific, Natick, MA) was placed in the feeding artery and inflated. The patient was heparinized during the procedure. Oversized stainless steel coils of 15-, 12-, and 10-mm diameter were placed in the feeding artery to form an “endoskeleton” or “scaffold.” Once the “scaffold” is formed, the occlusion balloon catheter is deflated and the 7/5 Lumax catheter is exchanged for it. Cross-sectional occlusion is obtained by nesting long platinum fibered coils within the “scaffold.” In (D, E), the final occlusion is demonstrated. In (F, G), an 8-month follow-up demonstrates no reperfusion. In patients with pulmonary hypertension, reperfusion is more common and it is our practice to perform a follow-up pulmonary angiogram at 6 months to 1 year. (Color version of figure is available online.)
Technical Suggestions We have identified a number of key practices that we believe contribute to technical success and significantly reduce complications. First, we have found it best to deliberate over options rather than to respond immediately, in elective patients with PAVMs in larger arteries. It is beneficial to perform a diagnostic angiogram first and then take time to evaluate the results and determine the most effective approach.3,11
We also recommend that wires always be withdrawn from catheters under saline. This prevents the possibility of air entering the catheter as the wire is withdrawn and avoids the potential of air emboli. In addition, regular flushing of catheters serves to reduce the potential for embolization of particular matter or clot. Before injecting contrast material or saline, we ensure that blood can be easily aspirated. If blood cannot be aspirated, move the catheter and test again before
Pulmonary arteriovenous malformations
289
Figure 4 (Continued)
attempting to flushing a catheter. Injection should never be attempted if blood cannot be aspirated.
Results Our results using pushable fibered coils are identical to our results using detachable balloons, with a recurrence rate of 3% per patient and 6% per PAVM. In our use of the anchor and scaffold techniques, we have not experienced paradoxical embolization of coil since 1994.11,12 It is important to note that enlargement of small PAVMs is more common than recurrence of treated PAVMs, occurring in
approximately 18% of patients.3 Most patients with recurrent or enlarged PAVMs are symptomatic; however, this is not always the case and some malformations are only identified with imaging. Therefore, noncontrast computed tomographic (chest computed tomography) evaluation of treated patients is necessary at the 1-year mark and every 5 years thereafter.3
Discussion Up until the early 1990s, thoracic surgeons advocated the surgical removal of PAVMs. In 1997, our group presented our results on
R.I. White
290 occlusion of large PAVMs to the Society of Thoracic Surgeons.11 Since then, embolization has effectively replaced surgery as the treatment of choice. A number of different materials have been used to embolize PAVMs, including detachable occlusion balloons, various types of fibered and unfibered, detachable, and pushable coils, and, most recently, the Amplatzer Vascular Plug (AGA Medical Corporation, Plymouth, MN).13 At the present time, detachable balloons are only available in Europe. They are made of latex with a gold-valve balloon (Nycomed, Paris, France). Published reports on the use of this device indicate problems with early deflation, leading to poor results.14 No other balloons have been available since 2002. The Amplatzer plug has become an attractive alternative among some interventional radiologists; however, the device is costly and long-term results are not yet available.15 There are good long-term data on the various types of fibered pushable coils.3,16 Nonfibered detachable microcoils have been advocated by some; however, they are expensive and do not offer an advantage over pushable fibered coils delivered with our guiding catheter approach.17
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References 1. White RI Jr, Pollak JS, Wirth JA: Pulmonary arteriovenous malformations: diagnosis and transcatheter embolotherapy. JVIR 7:787-804, 1996 2. Mager JJ, Overtoom TT, Blauw H, et al: Embolotherapy of pulmonary arteriovenous malformations: long-term results in 112 patients. J Vasc Interv Radiol 15:451-456, 2004 3. Pollak JS, Saluja S, Thabet A, et al: Clinical and anatomic outcomes after embolotherapy of pulmonary arteriovenous malformations. J Vasc Interv Radiol 17(1):35-45, 2006 4. Guttmacher AE, Marchuk DA, White RI Jr: Hereditary hemorrhagic telangiectasia. New Engl J Med 333:918-924, 1995 5. Hewes RC, Auster M, White RI Jr: Cerebral embolism: first manifestation of pulmonary arteriovenous malformation in patients with
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hereditary hemorrhagic telangiectasia. Cardiovasc Intervent Radiol 8:151-155, 1985 Moussouttas M, Fayad P, Rosenblatt M, et al: Pulmonary arteriovenous malformations: cerebral ischemia and neurologic manifestations. Neurology 55:959-964, 2000 Garcia-Tsao G, Korzenik JR, Young L, et al: Liver disease in patients with hereditary hemorrhagic telangiectasia. New Engl J Med 343(13): 931-936, 2000 Trembath RC, Thomson JR, Machado RD, et al: Clinical and molecular genetic features of pulmonary hypertension in patients with hereditary hemorrhagic telangiectasia. New Engl J Med 345(5):325-334, 2001 White RI Jr, Pollak JS: Controlled delivery of pushable fibered coils for large vessel embolotherapy, in: Vascular Ebolotherapy: A Comprehensive Approach. Springer, Heidelberg, Germany, 2006, pp 35-42 Tal MG, Saluja S, Henderson KJ, et al: Vein of Galen technique for occluding the aneurysmal sac of pulmonary arteriovenous malformations. J Vas Interv Radiol 13:1261-1264, 2002 Lee DW, White RI Jr, Egglin TK, et al: Embolotherapy of large pulmonary arteriovenous malformations—long term results. Ann Thorax Surg 64:930-940, 1997 Pollak JS, Saluja S, Thabet A, et al: Clinical and anatomic outcomes after embolotherapy of pulmonary arteriovenous malformations. J Vasc Interv Radiol 17:35-44, 2006 White RI Jr: Re: Bilateral multiple pulmonary arteriovenous malformations: endovascular treatment with the Amplatzer vascular plug. J Vasc Interv Radiol 17(1):141-145, 2006 Saluja S, Sitko I, Lee DW, et al: Embolotherapy of pulmonary arteriovenous malformations with detachable balloons: long-term durability and efficacy. J Vas Interv Radiol 10:883-889, 1999 Ferro C, Rossi UG, Bovio G, et al: Percutaneous transcatheter embolization of a large pulmonary arteriovenous fistula with an Amplatzer vascular plug. Cardiovasc Intervent Radiol 30(2):328-331, 2007 Mager JJ, Zanen P, Verzijlbergen F, et al: Quantification of right-to-left shunt with (99m)Tc-labelled albumin macroaggregates and 100% oxygen in patients with hereditary haemorrhagic telangiectasia. Clin Sci (Lond) 102(2):127-134, 2002 White RI Jr, Pollak JS, Picus D: Are Guglielmi detachable coils necessary for treating pulmonary arteriovenous malformations? Radiology 226(2):599-600, 2003